The proposed research is designed to provide a systematic investigation of a spectrally-oriented tactual aid for profoundly-deaf listeners. Toward this goal, we have designed, built, and are now testing a multi-point electrotactile speech aid (MESA-I) that is worn on the abdomen. MESA-I is a 288-point stimulator (36 columns x 8 rows) with frequency coded horizontally in space and amplitude coded vertically in space. The 36 frequency channels cover a range from 85 Hz to 10,500 Hz. Our current data demonstrate that, with training, vowels in a CVC context can be identified with near perfect accuracy, and the consonantal features of voicing and nasality, both of which are critical for deaf listeners, are well resolved. While data obtained using MESA-I represent better resolution for speech features than that demonstrated by any other spectrally-based aid, we believe that certain design changes will improve the ease with which vowels are differentiated, and improve the resolution of certain consonantal features. The most important proposed change in the transform is the restriction of MESA-I's 36 filters to the frequency region known to be critical to speech reception (300 Hz to 5 kHz). At present, only 20 of our 36 filters are located in this region and we expect that increasing the number of filters, particularly in the first and second formant regions, will improve the resolution of phonetic features which involve rapid spectral changes such as the feature place of articulation. We propose to test this second-generation device (MESA-II) on speech perception tasks as well as on basic psychophysical tasks using synthetic signals that are relevant to speech perception and that can be compared to data obtained in the auditory domain. The proposed speech testing involves an investigation of both phonetic and prosodic speech features in speech materials ranging from isolated syllables and words to sentences and connected discourse. The proposed psychophysical investigations include establishing the different limens (DL's) for fundamental frequency, and for the frequency and amplitude of the first three formants. In addition, the effects of backward, forward, and simultaneous masking will be investigated using synthetic signals which resemble consonant bursts and vowels.